This is the equivalent of 25 grams of sugar for women and 35 grams, or seven to eight teaspoonfuls, for men.

A single 330ml can of fizzy drink contains around seven teaspoonfuls, and so would meet this limit on its own.

Professor Ian Macdonald, who chaired the SACN carbohydrates working group, said: “One can will use up your 5%, but the message has got to be to reduce consumption of all sorts of foods and drinks.

“It is possible without it being a boring Second World War type of diet,” he said.

The guidance will go out for public consultation before a final report due to be published in March 2015.

Free sugars are those added to food or contained in fruit juices, honey, syrups and sweetened drinks. They do not include the sugars locked inside fresh fruits and vegetables, and milk.

The scientists also recommended an increase in daily total fibre intake from around 18 grams to 30 grams for adults.

Evidence shows that fibre improves bowel health and can help prevent heart disease.

Carbohydrates should make up half the population’s daily calorie intake, as recommended at present, said the committee.

The nutrition experts came to their conclusions after reviewing thousands of research papers from scientists investigating the health effects of sugar.

Too much sugar in the diet is known to be one of the primary reasons for the obesity epidemic and rising rates of Type 2 diabetes. Free sugar also poses a serious threat to dental health.

Dr Ann Prentice, chair of the SACN and director of human nutrition research at the Medical Research Council, said: “SACN has carried out a rigorous assessment of an extensive evidence base on the role of carbohydrates in the diet and their relationship to health.

“There is strong evidence in the report to show that if people were to have less free sugars and more fibre in their diet they would lower their risk of cardiovascular disease, Type 2 diabetes and bowel cancer,” she said

Ann Prentice

“For their health, people need to consume a balanced diet which includes carbohydrate-rich foods that are low in free sugars and high in fibre,” she added.

Public Health England said it was rising to the sugar challenge by ramping up its health campaigns and calling on consumers, food companies, retailers and other stakeholders to collaborate in tackling the issue.

Dr Alison Tedstone, chief nutritionist at Public Health England, stressed that for the time being, the current recommendation that free sugar should make up 10% of daily calories would remain in force.

She said: “We are very concerned about sugar intakes.. If you look at the dietary data you see that every single population group in England is exceeding the recommended intake for sugar.

“One of the reasons we’re worried is because of obesity. We tend to think of obesity as being a cosmetic problem, only to do with those images we see of grossly obese people. It’s not. Being a little bit overweight or podgy increases your risk of metabolic diseases.

“The situation in the UK is very difficult. We have over two thirds of the adult population being overweight or obese. One in five four to five-year-olds are obese or overweight. By the time they leave primary school, one in three are obese or overweight.”

She added that 28% of five-year-olds suffered from tooth decay in England. Soft drinks account for about 30% of children’s sugar intake, she noted.

Manufacturers’ claims that sweetened drinks only make up some 3% of sugar consumption were based on the whole population, not just children.

“It doesn’t mean having a very different diet. It means thinking about swapping these high-sugar foods for low-sugar alternatives”

Alison Tedstone

Speaking at a news briefing in London, Dr Tedstone said cutting sugar to 5% of calories simply meant making a lifestyle choice to limit consumption of food items such as fizzy drinks, chocolate, sweets, and cakes.

She stated: “It doesn’t mean having a very different diet. It means thinking about swapping these high-sugar foods for low-sugar alternatives; for example, drinking water. Instead of having a chocolate bar you could have a piece of fruit.”

Professor Graham MacGregor, chair of the group Action on Sugar, said: “We are currently consuming far above the current recommendations of 10%, so it is fantastic that this strong recommendation has been put forward and shows the urgency of acting now.

“He must start by setting targets for reducing sugar in soft drinks this summer and move responsibility for nutrition to an independent body such as the Food Standards Agency so that the soft drinks and food industry are given a level-playing field, with the threat of regulation to ensure the whole of the food industry comply.”